Crusaders boss Todd Blackadder has called for the rulebook to be tweaked after his side's loss to the Chiefs.
Reed Prinsep, the replacement Crusaders flanker, was knocked out and required around ten minutes of on-field assistance before leaving the field on a stretcher and going to hospital.
However the Crusaders were unable to send back on starting flanker Tim Boys due to a quirk in the rulebook.
Starting players are only allowed to be substituted back onto the field for blood injuries or for a concussion test, but because Prinsep was knocked unconsciousness the Crusaders were unable to bring Boys back on, replacing Prinsep instead with replacement half-back Leon Fukofuka instead.
"I think common sense needs to prevail here," Blackadder told the NZ Herald.
"If Reed had been able to say 'I've had a head knock, I need to come off for a concussion test', we would have been able to replace him with Tim. But the fact that he was knocked unconscious meant we weren't able to do that.
"The law needs to be amended straight away because player welfare has to come first and teams shouldn't be penalised for players being knocked unconscious."